Re: [PATCH] Fortran: reject procedures and procedure pointers as output item [PR107074]

[Mikael Morin <morin-mikael@orange.fr>]

Hello

Le 04/10/2022 à 21:27, Harald Anlauf via Fortran a écrit :
> Dear all,
> 
> when looking at output item lists we didn't catch procedures
> and procedure pointers and ran into a gfc_internal_error().
> Such items are not allowed by the Fortran standard, e.g. for
> procedure pointers there is
> 
> C1233 (R1217) An expression that is an output-item shall not
>                have a value that is a procedure pointer.
> 
> Attached patch generates an error instead.
> 
> Regtested on x86_64-pc-linux-gnu.  OK for mainline?
> 
Please move the check to resolve_transfer in resolve.cc.

Strangely, the patch doesn't seem to fix the problem on the testcase 
here.  There is an outer parenthese expression preventing the condition 
you added from triggering.  Can you double check?

If we take the standard to the letter, only output items are forbidden, 
so a check is missing for writing context.  I don't know how it can work 
for input items though, so maybe not worth it.  In any case, the error 
shouldn't mention output items in reading context.

Here is a variant of the testcase with procedure pointer components, 
that fails differently but can probably be caught as well.

program p
   implicit none
   type :: t
     procedure(f), pointer, nopass :: b
   end type t
   type(t) :: a

   interface
     real function f()
     end function f
   end interface

   print *, merge (a%b, a%b, .true.)
end